In the manufacture of a number of semiconductor devices on a wafer, photolithography steps and etching, thin film deposition, and/or ion implantation steps are alternately performed to build up the of the devices. The photolithography steps typically include steps of coating a wafer with a photoresist, typically an ultraviolet (UV) photosensitive organic material; exposing the photoresist through a mask; developing the resist; and etching the exposed resist to leave certain exposed areas on the wafer surface. Further processing steps, such as deposition, implantation, or etching can then be employed on the exposed areas.
Etching is typically performed with either a wet etching process in which the wafers are immersed in a chemical etchant; or a dry etching process, such as downstream microwave plasma etching or reactive ion etching (RIE). After photoresist is patterned on a surface and after further processing steps are performed in exposed areas, the photoresist is stripped.
Microwave downstream processing can be performed with atomic oxygen to strip resist when wafers cannot tolerate electrical damage. Because atomic oxygen is very chemically reactive, however, it can recombine very rapidly on the surface of a metal, such as aluminum that may be used in chambers for cleaning and stripping. The nature of these reactions, and the factors that influence the effects, are not well understood, so manufacturers have been discouraged from using aluminum chambers for microwave downstream ashing with atomic oxygen.